Centaurea stoebe subsp. micranthos (spotted knapweed) [Asteraceae] an invasive species in the southern Ozarks: Infested vs. non-infested sites and a ploidy level study

This study is an investigation of spotted knapweed (Centaurea stoebe subsp. micranthos), an invasive roadside plant, in the southern Ozark Plateau region. Studies consisted of an investigation into the geographical distribution of spotted knapweed in Arkansas, a comparison of community and environmental differences between infested and non-infested sites, an examination of environmental variables associated with spotted knapweed populations, and a ploidy level study. It was found that populations of spotted knapweed are spreading in the state, seven other plant species showed a negative correlation with spotted knapweed and spotted knapweed population levels display a pattern of increasing as slope increases. No other community or environmental differences were found between infested and non-infested sites and all populations studied were the tetraploid form (2n = 36). These results clearly indicate that spotted knapweed impacts the environment in this region and that control of this invasive plant is of the utmost importance.